Based on industry studies and ExxonMobil's own records for the Pegasus pipeline, the oil company knew or should have known the following six facts that help explain what went wrong in this year's oil spill in the North Woods neighborhood of Mayflower, Ark., a town of 2,300 people located about 20 miles northeast of Little Rock.

Risks of using an aging pipeline network for Canadian heavy oil, well-known to industry and discussed over many years, have never been addressed. The Exxon oil spill in Arkansas finally might change that.